Many athletes and non-athletes utilize weight lifting or weight training exercises to build strength and/or bulk, to prevent injury, or to improve overall condition and appearance. Typically, weight training exercises are performed with either exercise machines or free weights, i.e., barbells and weighted plates, dumbbells, etc. For various reasons, most exercise programs incorporate both machines and free weights in a variety of different exercise routines to maximize the effect of working out a desired number of muscle groups.
One exercise maneuver that is frequently performed on an exercise machine is referred to as a leg curl. The leg curl exercise is performed from a prone, face down position and involves the bending, against a pivotal weight resistance, of one leg or both legs from a straight, extended position to a flexed position. During the exercise, the applied force of the legs is directed against pads connected to a pivotal lever. At the end of the exercise, when the legs are flexed, the pads reside between the back of the hamstrings and the Achilles tendons of the exerciser. Removable weights, or a stationary stack of weights are connectable to the lever to provide a selectable weight resistance that is exercised against.
There are presently a number of different machines available for performing a leg curl exercise. Some leg curl machines simply utilize a lever pivotally connected to a frame that includes a horizontal support, with removable weights supported on the lever. While relatively simple in construction, these machines are rather awkward for the exerciser because the horizontal support does not provide good leverage for performing the leg curl motion. Moreover, the support must remain substantially flat because these particular machines are generally also used for performing a leg extension exercise from a seated, forward-facing position on the platform.
Other leg curl exercise machines utilize a pulley and cable to direct the exercise movement against the weight resistance. At least one leg curl machine uses an eccentric cam and chain mechanism for the same purpose. Leg curl machines which utilize a cable/chain linkage require periodic maintenance to prevent friction buildup which effectively results in an undesired increase in weight resistance that acts against the leg curl movement. Moreover, the additional parts required by cable/chain linkage machines are also susceptible to wearing out or functioning improperly, thus necessitating removal and repair.
Perhaps more importantly, these other leg curl machines do not always feel right or "fit" the body properly. For instance, structural components such as the pivot point or the lever length seem to be sized disproportionately for a large number of athletes. While some portion of this awkwardness may be attributable to the fact that most exercise machines are sized or shaped for an "average" size person and many people who use these machines are simply not of "average" musculoskeletal structure, there is also another degree of awkwardness which does not seem to be size-related at all. This latter degree of awkwardness relates to unnatural musculoskeletal positioning that results directly from the orientation of the machine itself, even for an average size individual. As a result, muscles, bones and/or joints are subjected to unnecessary shear or compression stress during the performance of exercise with these machines. Moreover, the maximum muscular benefit is not achieved.
These disadvantages are particularly unfortunate in the case of both the leg curl exercise and the leg extension exercise because these complementary exercises work opposing muscle groups that are considered critical to minimizing the risk of injury to the knee joint, one of the body's most susceptible joints.
Finally, if the knee is injured, it is considered important to perform the leg curl and the leg extension exercises with one leg only during rehabilitation, to allow close monitoring of progress. Unfortunately, single leg performance of a leg curl exercise on most prior machines seems to accentuate the awkwardness or uncomfortable fit of the machine.
It is therefore an object of the invention to provide a leg curl exercise machine that maximizes the exercise benefit attainable during a leg curl maneuver while minimizing skeletal or joint stress associated therewith.
It is another object of the invention to provide a leg curl exercise machine that reduces or eliminates the unnatural feel that seems to be inherent with other leg curl exercise machines.
It is still another object of the invention to provide a leg curl exercise machine which is particularly suitable for exercising one leg at a time.